A camera is a device that captures an image or scene by optically projecting it onto a sensing device in a focal plane. A film camera exposes a light-sensitive film placed on the focal plane to the projected image for a period of time in order to record the image. Over the years, both still and moving film cameras have used a variety of film sizes and aspect ratios. Although in the early days of cameras, film was often cut to size, most film today is provided in film strips which are advanced inside the camera to place an unused portion in the focal plane. A masking device inside the camera prevents the light from a projected image from exposing film outside the mask. Substantially all of the masks (and the cut film before that) are rectangular or square.
Newer digital cameras use a photosensitive array of photocells in a manner similar to that of film. As with film, the array is located on the focal plane and exposed to the projected image for a period of time in order to capture the image. Unlike film, however, the array may remain stationary. Once the image is captured using the array, it can be stored in a computer memory and recorded on any digital media.
Arrays of photocells are typically manufactured as rectangles, with a typical ratio of 3:4 between the long and short edges. Images of interest, however, may not be 3:4 rectangles, and are often nonrectangular at all. Conventional film and digital cameras capture non-rectangular images of interest by using only part of the frame for the image, and essentially wasting the remainder of the frame (e.g., film or memory) on the portion thereof that is not of interest.
Existing cameras typically have photocells comprising over 1 million pixels, and often 5 million or more. Even in the consumer market today, it is not uncommon to find still cameras having over 10 million pixels. Each pixel can provide a single point of color or black-and-white resolution, and often each pixel is capable of representing one of many millions of colors. Accordingly, in a raw format, a six mega-pixel photocell with 24-bits per pixel can require as much as 18 megabytes of data per frame of captured image.
Some existing cameras can programmably change the resolution of the image by diluting the pixels or by combining adjacent pixels. Data compression techniques, are available for reducing the amount of data required for each frame. For example, for moving pictures, MPEG, which stands for Moving Picture Experts Group, is the name of family of standards used for coding audio-visual information (e.g., movies, video, music) in a digital compressed format. For still pictures, the JPEG format is available. JPEG compresses graphics of photographic color depth, which makes the images smaller. With either of these techniques, the image deteriorates in quality as one adds compression.
In any event, JPEG and MPEG type compression requires substantial data processing power. Thus, in order to capture an image of interest at a desired resolution, a camera requires a large memory and large bandwidth data transport for storing frame data in that memory. Alternatively, where some (often programmable) loss of resolution or clarity is acceptable, the camera still requires substantial data processing power for compression that is continuously available at the maximum frame rate of the camera.
What is needed is a camera that can reduce the memory and bandwidth required, but still provide an image of interest without undesired loss of clarity.